* [PATCH 4/4] arch/powerpc/44x/fsp2: wdt tcr update instead of whole rewrite @ 2017-05-15 13:07 Ivan Mikhaylov 2017-05-19 10:24 ` Michael Ellerman 2017-05-19 10:30 ` [PATCH 4/4] " Benjamin Herrenschmidt 0 siblings, 2 replies; 9+ messages in thread From: Ivan Mikhaylov @ 2017-05-15 13:07 UTC (permalink / raw) To: Alistair Popple, Matt Porter Cc: linuxppc-dev, linux-kernel, Benjamin Herrenschmidt, Joel Stanley, Paul Mackerras, Michael Ellerman Prevent a kernel panic caused by unintentionally clearing TCR watchdog bits. At this point in the kernel boot, the watchdog has already been enabled by u-boot. The original code's attempt to write to the TCR register results in an inadvertent clearing of the watchdog configuration bits, causing the 476 to reset. Panic happens in case of error as silently reboot without any outputs on serial. Signed-off-by: Ivan Mikhaylov <ivan@de.ibm.com> --- arch/powerpc/kernel/time.c | 16 ++++++++++++++++ 1 files changed, 16 insertions(+), 0 deletions(-) diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 2b33cfa..f75e512 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -738,12 +738,28 @@ static int __init get_freq(char *name, int cells, unsigned long *val) static void start_cpu_decrementer(void) { + unsigned int tcr; #if defined(CONFIG_BOOKE) || defined(CONFIG_40x) /* Clear any pending timer interrupts */ mtspr(SPRN_TSR, TSR_ENW | TSR_WIS | TSR_DIS | TSR_FIS); +#ifdef CONFIG_FSP2 + /* + * Prevent a kernel panic caused by unintentionally clearing TCR + * watchdog bits. At this point in the kernel boot, the watchdog has + * already been enabled by u-boot. The original code's attempt to + * write to the TCR register results in an inadvertent clearing of the + * watchdog configuration bits, causing the 440 to reset. + */ + tcr = mfspr(SPRN_TCR); + tcr &= TCR_WP_MASK; /* clear all bits except for TCR[WP] */ + tcr |= TCR_DIE; /* enable decrementer */ + mtspr(SPRN_TCR, tcr); +#else /* Enable decrementer interrupt */ mtspr(SPRN_TCR, TCR_DIE); +#endif + #endif /* defined(CONFIG_BOOKE) || defined(CONFIG_40x) */ } -- 1.7.1 ^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH 4/4] arch/powerpc/44x/fsp2: wdt tcr update instead of whole rewrite 2017-05-15 13:07 [PATCH 4/4] arch/powerpc/44x/fsp2: wdt tcr update instead of whole rewrite Ivan Mikhaylov @ 2017-05-19 10:24 ` Michael Ellerman 2017-05-19 10:30 ` [PATCH 4/4] " Benjamin Herrenschmidt 1 sibling, 0 replies; 9+ messages in thread From: Michael Ellerman @ 2017-05-19 10:24 UTC (permalink / raw) To: Ivan Mikhaylov, Alistair Popple, Matt Porter Cc: linuxppc-dev, linux-kernel, Benjamin Herrenschmidt, Joel Stanley, Paul Mackerras Hi Ivan, Ivan Mikhaylov <ivan@de.ibm.com> writes: > Prevent a kernel panic caused by unintentionally clearing TCR > watchdog bits. At this point in the kernel boot, the watchdog has > already been enabled by u-boot. The original code's attempt to > write to the TCR register results in an inadvertent clearing of the > watchdog configuration bits, causing the 476 to reset. > Panic happens in case of error as silently reboot without any outputs > on serial. That sounds reasonable. > diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c > index 2b33cfa..f75e512 100644 > --- a/arch/powerpc/kernel/time.c > +++ b/arch/powerpc/kernel/time.c > @@ -738,12 +738,28 @@ static int __init get_freq(char *name, int cells, unsigned long *val) > > static void start_cpu_decrementer(void) > { > + unsigned int tcr; > #if defined(CONFIG_BOOKE) || defined(CONFIG_40x) > /* Clear any pending timer interrupts */ > mtspr(SPRN_TSR, TSR_ENW | TSR_WIS | TSR_DIS | TSR_FIS); > > +#ifdef CONFIG_FSP2 > + /* > + * Prevent a kernel panic caused by unintentionally clearing TCR > + * watchdog bits. At this point in the kernel boot, the watchdog has > + * already been enabled by u-boot. The original code's attempt to Don't refer to "the original code", as it doesn't exist anymore now that we've patched it. Just say something like ".. so we must not clear the watchdog configuration bits". > + * write to the TCR register results in an inadvertent clearing of the > + * watchdog configuration bits, causing the 440 to reset. > + */ > + tcr = mfspr(SPRN_TCR); > + tcr &= TCR_WP_MASK; /* clear all bits except for TCR[WP] */ > + tcr |= TCR_DIE; /* enable decrementer */ > + mtspr(SPRN_TCR, tcr); > +#else > /* Enable decrementer interrupt */ > mtspr(SPRN_TCR, TCR_DIE); > +#endif > + > #endif /* defined(CONFIG_BOOKE) || defined(CONFIG_40x) */ That breaks the build for other platforms: arch/powerpc/kernel/time.c: In function ‘start_cpu_decrementer’: arch/powerpc/kernel/time.c:741:15: error: unused variable ‘tcr’ [-Werror=unused-variable] You can just do something like: #if defined(CONFIG_BOOKE) || defined(CONFIG_40x) unsigned int tcr; #ifdef CONFIG_FSP2 tcr = mfspr(SPRN_TCR); tcr &= TCR_WP_MASK; /* clear all bits except for TCR[WP] */ #else tcr = 0; #endif tcr |= TCR_DIE; /* enable decrementer */ mtspr(SPRN_TCR, TCR_DIE); #endif /* defined(CONFIG_BOOKE) || defined(CONFIG_40x) */ Or you could possibly just always leave TCR[WP], is there any case where it would be correct to clear that? cheers ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 4/4] arch/powerpc/44x/fsp2: wdt tcr update instead of whole rewrite @ 2017-05-19 10:24 ` Michael Ellerman 0 siblings, 0 replies; 9+ messages in thread From: Michael Ellerman @ 2017-05-19 10:24 UTC (permalink / raw) To: Ivan Mikhaylov, Alistair Popple, Matt Porter Cc: linuxppc-dev, linux-kernel, Benjamin Herrenschmidt, Joel Stanley, Paul Mackerras Hi Ivan, Ivan Mikhaylov <ivan@de.ibm.com> writes: > Prevent a kernel panic caused by unintentionally clearing TCR > watchdog bits. At this point in the kernel boot, the watchdog has > already been enabled by u-boot. The original code's attempt to > write to the TCR register results in an inadvertent clearing of the > watchdog configuration bits, causing the 476 to reset. > Panic happens in case of error as silently reboot without any outputs > on serial. That sounds reasonable. > diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c > index 2b33cfa..f75e512 100644 > --- a/arch/powerpc/kernel/time.c > +++ b/arch/powerpc/kernel/time.c > @@ -738,12 +738,28 @@ static int __init get_freq(char *name, int cells, u= nsigned long *val) >=20=20 > static void start_cpu_decrementer(void) > { > + unsigned int tcr; > #if defined(CONFIG_BOOKE) || defined(CONFIG_40x) > /* Clear any pending timer interrupts */ > mtspr(SPRN_TSR, TSR_ENW | TSR_WIS | TSR_DIS | TSR_FIS); >=20=20 > +#ifdef CONFIG_FSP2 > + /* > + * Prevent a kernel panic caused by unintentionally clearing TCR > + * watchdog bits. At this point in the kernel boot, the watchdog has > + * already been enabled by u-boot. The original code's attempt to Don't refer to "the original code", as it doesn't exist anymore now that we've patched it. Just say something like ".. so we must not clear the watchdog configuration bits". > + * write to the TCR register results in an inadvertent clearing of the > + * watchdog configuration bits, causing the 440 to reset. > + */ > + tcr =3D mfspr(SPRN_TCR); > + tcr &=3D TCR_WP_MASK; /* clear all bits except for TCR[WP] */ > + tcr |=3D TCR_DIE; /* enable decrementer */ > + mtspr(SPRN_TCR, tcr); > +#else > /* Enable decrementer interrupt */ > mtspr(SPRN_TCR, TCR_DIE); > +#endif > + > #endif /* defined(CONFIG_BOOKE) || defined(CONFIG_40x) */ That breaks the build for other platforms: arch/powerpc/kernel/time.c: In function =E2=80=98start_cpu_decrementer=E2= =80=99: arch/powerpc/kernel/time.c:741:15: error: unused variable =E2=80=98tcr=E2= =80=99 [-Werror=3Dunused-variable] You can just do something like: #if defined(CONFIG_BOOKE) || defined(CONFIG_40x) unsigned int tcr; #ifdef CONFIG_FSP2 tcr =3D mfspr(SPRN_TCR); tcr &=3D TCR_WP_MASK; /* clear all bits except for TCR[WP] */ #else tcr =3D 0; #endif tcr |=3D TCR_DIE; /* enable decrementer */ mtspr(SPRN_TCR, TCR_DIE); #endif /* defined(CONFIG_BOOKE) || defined(CONFIG_40x) */ Or you could possibly just always leave TCR[WP], is there any case where it would be correct to clear that? cheers ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 4/4] arch/powerpc/44x/fsp2: wdt tcr update instead of whole rewrite 2017-05-19 10:24 ` Michael Ellerman @ 2017-05-19 15:47 ` Ivan Mikhaylov -1 siblings, 0 replies; 9+ messages in thread From: Ivan Mikhaylov @ 2017-05-19 15:47 UTC (permalink / raw) To: Michael Ellerman, Alistair Popple, Matt Porter Cc: linuxppc-dev, linux-kernel, Benjamin Herrenschmidt, Joel Stanley, Paul Mackerras Hi Michael, >> diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c >> index 2b33cfa..f75e512 100644 >> --- a/arch/powerpc/kernel/time.c >> +++ b/arch/powerpc/kernel/time.c >> @@ -738,12 +738,28 @@ static int __init get_freq(char *name, int cells, unsigned long *val) >> >> static void start_cpu_decrementer(void) >> { >> + unsigned int tcr; >> #if defined(CONFIG_BOOKE) || defined(CONFIG_40x) >> /* Clear any pending timer interrupts */ >> mtspr(SPRN_TSR, TSR_ENW | TSR_WIS | TSR_DIS | TSR_FIS); >> >> +#ifdef CONFIG_FSP2 >> + /* >> + * Prevent a kernel panic caused by unintentionally clearing TCR >> + * watchdog bits. At this point in the kernel boot, the watchdog has >> + * already been enabled by u-boot. The original code's attempt to > > Don't refer to "the original code", as it doesn't exist anymore now that > we've patched it. Just say something like ".. so we must not clear the > watchdog configuration bits". Ok, got it. >That breaks the build for other platforms: > > arch/powerpc/kernel/time.c: In function ‘start_cpu_decrementer’: > arch/powerpc/kernel/time.c:741:15: error: unused variable ‘tcr’ [-Werror=unused-variable] > Oops, didn't notice, my fault. >Or you could possibly just always leave TCR[WP], is there any case where >it would be correct to clear that? > >cheers >From my point of view it's possible. I've checked docu and on idea it should be possible cause WP is only affecting watchdog ping time. Which in case of '00' is very small, around ~5 ms. Ben also in next message said about get rid of ifdef for FSP2. And now patch looks like this, What do you think Michael, Ben? arch/powerpc/kernel/time.c | 15 +++++++++++++-- 1 files changed, 13 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index bc2e08d..2411c49 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -718,11 +718,22 @@ static int __init get_freq(char *name, int cells, unsigned long *val) static void start_cpu_decrementer(void) { #if defined(CONFIG_BOOKE) || defined(CONFIG_40x) + unsigned int tcr; /* Clear any pending timer interrupts */ mtspr(SPRN_TSR, TSR_ENW | TSR_WIS | TSR_DIS | TSR_FIS); - /* Enable decrementer interrupt */ - mtspr(SPRN_TCR, TCR_DIE); + tcr = mfspr(SPRN_TCR); + /* + * At this point in the kernel boot, the watchdog has already + * been enabled by u-boot. If we set it this to '00' it may + * trigger watchdog earlier than needed which will cause + * inattentional kernel panic. In this case we leaving TCR[WP] + * bit setting from uboot/bootstrap. + */ + tcr &= TCR_WP_MASK; /* clear all bits except for TCR[WP] */ + tcr |= TCR_DIE; /* enable decrementer */ + mtspr(SPRN_TCR, tcr); + #endif /* defined(CONFIG_BOOKE) || defined(CONFIG_40x) */ } -- 1.7.1 ^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH 4/4] arch/powerpc/44x/fsp2: wdt tcr update instead of whole rewrite @ 2017-05-19 15:47 ` Ivan Mikhaylov 0 siblings, 0 replies; 9+ messages in thread From: Ivan Mikhaylov @ 2017-05-19 15:47 UTC (permalink / raw) To: Michael Ellerman, Alistair Popple, Matt Porter Cc: linuxppc-dev, linux-kernel, Benjamin Herrenschmidt, Joel Stanley, Paul Mackerras Hi Michael, >> diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c >> index 2b33cfa..f75e512 100644 >> --- a/arch/powerpc/kernel/time.c >> +++ b/arch/powerpc/kernel/time.c >> @@ -738,12 +738,28 @@ static int =5F=5Finit get=5Ffreq(char *name, int c= ells, unsigned long *val) >> =20 >> static void start=5Fcpu=5Fdecrementer(void) >> { >> + unsigned int tcr; >> #if defined(CONFIG=5FBOOKE) || defined(CONFIG=5F40x) >> /* Clear any pending timer interrupts */ >> mtspr(SPRN=5FTSR, TSR=5FENW | TSR=5FWIS | TSR=5FDIS | TSR=5FFIS); >> =20 >> +#ifdef CONFIG=5FFSP2 >> + /* >> + * Prevent a kernel panic caused by unintentionally clearing TCR >> + * watchdog bits. At this point in the kernel boot, the watchdog has >> + * already been enabled by u-boot. The original code's attempt to > > Don't refer to "the original code", as it doesn't exist anymore now that > we've patched it. Just say something like ".. so we must not clear the > watchdog configuration bits". Ok, got it. >That breaks the build for other platforms: > > arch/powerpc/kernel/time.c: In function =E2=80=98start=5Fcpu=5Fdecremente= r=E2=80=99: > arch/powerpc/kernel/time.c:741:15: error: unused variable =E2=80=98tcr=E2= =80=99 [-Werror=3Dunused-variable] > Oops, didn't notice, my fault.=20 >Or you could possibly just always leave TCR[WP], is there any case where >it would be correct to clear that? > >cheers >From my point of view it's possible. I've checked docu and on idea it should be possible cause WP is only affecting watchdog ping time. Which in case of '00' is very small, around ~5 ms.=20 Ben also in next message said about get rid of ifdef for FSP2. And now patch looks like this, What do you think Michael, Ben? arch/powerpc/kernel/time.c | 15 +++++++++++++-- 1 files changed, 13 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index bc2e08d..2411c49 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -718,11 +718,22 @@ static int =5F=5Finit get=5Ffreq(char *name, int cell= s, unsigned long *val) static void start=5Fcpu=5Fdecrementer(void) { #if defined(CONFIG=5FBOOKE) || defined(CONFIG=5F40x) + unsigned int tcr; /* Clear any pending timer interrupts */ mtspr(SPRN=5FTSR, TSR=5FENW | TSR=5FWIS | TSR=5FDIS | TSR=5FFIS); =20 - /* Enable decrementer interrupt */ - mtspr(SPRN=5FTCR, TCR=5FDIE); + tcr =3D mfspr(SPRN=5FTCR); + /* + * At this point in the kernel boot, the watchdog has already + * been enabled by u-boot. If we set it this to '00' it may + * trigger watchdog earlier than needed which will cause + * inattentional kernel panic. In this case we leaving TCR[WP] + * bit setting from uboot/bootstrap. + */ + tcr &=3D TCR=5FWP=5FMASK; /* clear all bits except for TCR[WP] */ + tcr |=3D TCR=5FDIE; /* enable decrementer */ + mtspr(SPRN=5FTCR, tcr); + #endif /* defined(CONFIG=5FBOOKE) || defined(CONFIG=5F40x) */ } =20 --=20 1.7.1 ^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [PATCH 4/4] arch/powerpc/44x/fsp2: wdt tcr update instead of whole rewrite 2017-05-19 15:47 ` Ivan Mikhaylov (?) @ 2017-05-23 4:09 ` Michael Ellerman 2017-05-26 10:37 ` Michael Ellerman -1 siblings, 1 reply; 9+ messages in thread From: Michael Ellerman @ 2017-05-23 4:09 UTC (permalink / raw) To: Ivan Mikhaylov, Alistair Popple, Matt Porter Cc: linuxppc-dev, linux-kernel, Benjamin Herrenschmidt, Joel Stanley, Paul Mackerras Ivan Mikhaylov <ivan@de.ibm.com> writes: > > From my point of view it's possible. I've checked docu and on idea > it should be possible cause WP is only affecting watchdog ping time. The question is, is there any chance that leaving those bits set on another platform will cause a problem? ie. on existing machines we always clear those bits, is it OK that we will now start leaving those bits with whatever value they had. cheers ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 4/4] arch/powerpc/44x/fsp2: wdt tcr update instead of whole rewrite 2017-05-23 4:09 ` Michael Ellerman @ 2017-05-26 10:37 ` Michael Ellerman 0 siblings, 0 replies; 9+ messages in thread From: Michael Ellerman @ 2017-05-26 10:37 UTC (permalink / raw) To: Ivan Mikhaylov, Alistair Popple, Matt Porter Cc: linuxppc-dev, linux-kernel, Paul Mackerras, Joel Stanley Michael Ellerman <mpe@ellerman.id.au> writes: > Ivan Mikhaylov <ivan@de.ibm.com> writes: >> >> From my point of view it's possible. I've checked docu and on idea >> it should be possible cause WP is only affecting watchdog ping time. > > The question is, is there any chance that leaving those bits set on > another platform will cause a problem? > > ie. on existing machines we always clear those bits, is it OK that we > will now start leaving those bits with whatever value they had. I came up with the patch below (more or less your v2), if it breaks something we can always fix it. cheers commit c80409358a9c91e1f6b18353dad939b851bb3522 Author: Ivan Mikhaylov <ivan@de.ibm.com> Date: Fri May 19 18:47:05 2017 +0300 powerpc/[booke|4xx]: Don't clobber TCR[WP] when setting TCR[DIE] Prevent a kernel panic caused by unintentionally clearing TCR watchdog bits. At this point in the kernel boot, the watchdog may have already been enabled by u-boot. The original code's attempt to write to the TCR register results in an inadvertent clearing of the watchdog configuration bits, causing the 476 to reset. Signed-off-by: Ivan Mikhaylov <ivan@de.ibm.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 2b33cfaac7b8..60714b8c9a2f 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -739,12 +739,20 @@ static int __init get_freq(char *name, int cells, unsigned long *val) static void start_cpu_decrementer(void) { #if defined(CONFIG_BOOKE) || defined(CONFIG_40x) + unsigned int tcr; + /* Clear any pending timer interrupts */ mtspr(SPRN_TSR, TSR_ENW | TSR_WIS | TSR_DIS | TSR_FIS); - /* Enable decrementer interrupt */ - mtspr(SPRN_TCR, TCR_DIE); -#endif /* defined(CONFIG_BOOKE) || defined(CONFIG_40x) */ + tcr = mfspr(SPRN_TCR); + /* + * The watchdog may have already been enabled by u-boot. So leave + * TRC[WP] (Watchdog Period) alone. + */ + tcr &= TCR_WP_MASK; /* Clear all bits except for TCR[WP] */ + tcr |= TCR_DIE; /* Enable decrementer */ + mtspr(SPRN_TCR, tcr); +#endif } void __init generic_calibrate_decr(void) ^ permalink raw reply related [flat|nested] 9+ messages in thread
* Re: [4/4] arch/powerpc/44x/fsp2: wdt tcr update instead of whole rewrite 2017-05-19 15:47 ` Ivan Mikhaylov (?) (?) @ 2017-05-30 9:11 ` Michael Ellerman -1 siblings, 0 replies; 9+ messages in thread From: Michael Ellerman @ 2017-05-30 9:11 UTC (permalink / raw) To: Ivan Mikhaylov, Alistair Popple, Matt Porter Cc: linuxppc-dev, linux-kernel, Paul Mackerras, Joel Stanley [-- Warning: decoded text below may be mangled, UTF-8 assumed --] [-- Attachment #1: Type: text/plain, Size: 3138 bytes --] On Fri, 2017-05-19 at 15:47:05 UTC, Ivan Mikhaylov wrote: > Hi Michael, > > >> diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c > >> index 2b33cfa..f75e512 100644 > >> --- a/arch/powerpc/kernel/time.c > >> +++ b/arch/powerpc/kernel/time.c > >> @@ -738,12 +738,28 @@ static int __init get_freq(char *name, int cells, unsigned long *val) > >> > >> static void start_cpu_decrementer(void) > >> { > >> + unsigned int tcr; > >> #if defined(CONFIG_BOOKE) || defined(CONFIG_40x) > >> /* Clear any pending timer interrupts */ > >> mtspr(SPRN_TSR, TSR_ENW | TSR_WIS | TSR_DIS | TSR_FIS); > >> > >> +#ifdef CONFIG_FSP2 > >> + /* > >> + * Prevent a kernel panic caused by unintentionally clearing TCR > >> + * watchdog bits. At this point in the kernel boot, the watchdog has > >> + * already been enabled by u-boot. The original code's attempt to > > > > Don't refer to "the original code", as it doesn't exist anymore now that > > we've patched it. Just say something like ".. so we must not clear the > > watchdog configuration bits". > Ok, got it. > > >That breaks the build for other platforms: > > > > arch/powerpc/kernel/time.c: In function ‘start_cpu_decrementer’: > > arch/powerpc/kernel/time.c:741:15: error: unused variable ‘tcr’ [-Werror=unused-variable] > > > Oops, didn't notice, my fault. > > >Or you could possibly just always leave TCR[WP], is there any case where > >it would be correct to clear that? > > > >cheers > > >From my point of view it's possible. I've checked docu and on idea > it should be possible cause WP is only affecting watchdog ping time. > Which in case of '00' is very small, around ~5 ms. > Ben also in next message said about get rid of ifdef for FSP2. > > And now patch looks like this, What do you think Michael, Ben? > > arch/powerpc/kernel/time.c | 15 +++++++++++++-- > 1 files changed, 13 insertions(+), 2 deletions(-) > > diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c > index bc2e08d..2411c49 100644 > --- a/arch/powerpc/kernel/time.c > +++ b/arch/powerpc/kernel/time.c > @@ -718,11 +718,22 @@ static int __init get_freq(char *name, int cells, unsigned long *val) > static void start_cpu_decrementer(void) > { > #if defined(CONFIG_BOOKE) || defined(CONFIG_40x) > + unsigned int tcr; > /* Clear any pending timer interrupts */ > mtspr(SPRN_TSR, TSR_ENW | TSR_WIS | TSR_DIS | TSR_FIS); > > - /* Enable decrementer interrupt */ > - mtspr(SPRN_TCR, TCR_DIE); > + tcr = mfspr(SPRN_TCR); > + /* > + * At this point in the kernel boot, the watchdog has already > + * been enabled by u-boot. If we set it this to '00' it may > + * trigger watchdog earlier than needed which will cause > + * inattentional kernel panic. In this case we leaving TCR[WP] > + * bit setting from uboot/bootstrap. > + */ > + tcr &= TCR_WP_MASK; /* clear all bits except for TCR[WP] */ > + tcr |= TCR_DIE; /* enable decrementer */ > + mtspr(SPRN_TCR, tcr); > + > #endif /* defined(CONFIG_BOOKE) || defined(CONFIG_40x) */ > } > Applied to powerpc next, thanks. https://git.kernel.org/powerpc/c/6e2f03e292ef46eed2b31b0a344a91 cheers ^ permalink raw reply [flat|nested] 9+ messages in thread
* Re: [PATCH 4/4] arch/powerpc/44x/fsp2: wdt tcr update instead of whole rewrite 2017-05-15 13:07 [PATCH 4/4] arch/powerpc/44x/fsp2: wdt tcr update instead of whole rewrite Ivan Mikhaylov 2017-05-19 10:24 ` Michael Ellerman @ 2017-05-19 10:30 ` Benjamin Herrenschmidt 1 sibling, 0 replies; 9+ messages in thread From: Benjamin Herrenschmidt @ 2017-05-19 10:30 UTC (permalink / raw) To: Ivan Mikhaylov, Alistair Popple, Matt Porter Cc: linuxppc-dev, linux-kernel, Joel Stanley, Paul Mackerras, Michael Ellerman On Mon, 2017-05-15 at 16:07 +0300, Ivan Mikhaylov wrote: > +#ifdef CONFIG_FSP2 > + /* > + * Prevent a kernel panic caused by unintentionally clearing TCR > + * watchdog bits. At this point in the kernel boot, the watchdog has > + * already been enabled by u-boot. The original code's attempt to > + * write to the TCR register results in an inadvertent clearing of the > + * watchdog configuration bits, causing the 440 to reset. > + */ > + tcr = mfspr(SPRN_TCR); > + tcr &= TCR_WP_MASK; /* clear all bits except for TCR[WP] */ > + tcr |= TCR_DIE; /* enable decrementer */ > + mtspr(SPRN_TCR, tcr); > +#else This should be a runtime test, not a compile time option. Cheers, Ben. ^ permalink raw reply [flat|nested] 9+ messages in thread
end of thread, other threads:[~2017-05-30 9:11 UTC | newest] Thread overview: 9+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2017-05-15 13:07 [PATCH 4/4] arch/powerpc/44x/fsp2: wdt tcr update instead of whole rewrite Ivan Mikhaylov 2017-05-19 10:24 ` Michael Ellerman 2017-05-19 10:24 ` Michael Ellerman 2017-05-19 15:47 ` Ivan Mikhaylov 2017-05-19 15:47 ` Ivan Mikhaylov 2017-05-23 4:09 ` Michael Ellerman 2017-05-26 10:37 ` Michael Ellerman 2017-05-30 9:11 ` [4/4] " Michael Ellerman 2017-05-19 10:30 ` [PATCH 4/4] " Benjamin Herrenschmidt
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